Why are ghosts all sisters

In myths, ghosts are a product after death. But the real situation is... "Why do I want to work? I am obviously a ghost!" On the street, a half-loli girl wearing white sportswear with a strange pattern on her face shouted angrily. As if they couldn't see her, everyone around them turned a deaf ear to her shouts, but the young man in front of her reacted. "Assassin's Origin will be released soon, you can figure it out by yourself." The man left this sentence expressionlessly and then turned and left, leaving only a half-loli messy in the wind.